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What is phenobarbital?

Phenobarbital is in a group of drugs called barbiturates (bar-BIT-chur-ates). Phenobarbital slows the activity of your brain and nervous system.

Phenobarbital is used to treat or prevent seizures. It is also used short-term to treat insomnia, or as a sedative before surgery.

Phenobarbital may also be used for other purposes not listed in this medication guide.

Precautions

Instructions

Side-effects

Interactions

Precautions

Some people using this medicine have engaged in activity such as driving, eating, or making phone calls and later having no memory of the activity. If this happens to you, stop taking phenobarbital and talk with your doctor about another treatment for your sleep disorder.

Do not take this medication if you are allergic to phenobarbital, or if you have porphyria.

Before taking phenobarbital, tell your doctor if you are allergic to any drugs, or if you have:

• severe asthma, chronic obstructive pulmonary disorder (COPD), or other breathing disorder;
• liver disease;
• kidney disease;
• an adrenal gland disorder, such as pheochromocytoma;
• a history of depression, mental illness, or suicide attempt; or
• a history of drug or alcohol addiction.

If you have any of these conditions, you may need a dose adjustment or special tests to safely take phenobarbital.

Phenobarbital may be habit-forming and should be used only by the person it was prescribed for. Phenobarbital should never be shared with another person, especially someone who has a history of drug abuse or addiction. Keep the medication in a secure place where others cannot get to it.

Do not use this medication without telling your doctor if you are pregnant. It could cause harm to the unborn baby. Use an effective form of birth control, and tell your doctor if you become pregnant during treatment.

Phenobarbital can make birth control pills less effective. Ask your doctor about using a non-hormone method of birth control (such as a condom, diaphragm, spermicide) to prevent pregnancy while taking phenobarbital.

Phenobarbital can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Phenobarbital can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

Avoid using other medicines that make you sleepy (such as cold medicine, sleeping pills, pain medication, muscle relaxers, and medicine to treat depression or anxiety). They can add to sleepiness caused by phenobarbital.

Avoid drinking alcohol. It can increase some of the side effects of phenobarbital.

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Instructions

Seek emergency medical attention if you think you have used too much of this medicine. An overdose of phenobarbital can be fatal.

Overdose symptoms may include slow or shallow breathing, blurred vision, extreme drowsiness, urinating less than usual or not at all, feeling light-headed, or fainting.

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

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Side-effects

Phenobarbital may cause a severe allergic reaction. Stop taking phenobarbital and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• restless muscle movements in your eyes, tongue, jaw, or neck;
• slow heartbeat, shallow breathing;
• feeling light-headed, fainting;
• a fever or a sore throat;
• sores in your mouth;
• easy bruising or bleeding; or
• broken blood vessels under your skin.

Less serious side effects may include:

• drowsiness or dizziness;
• problems with memory or concentration;
• excitement, irritability, aggression, or confusion (especially in children or older adults);
• loss of balance or coordination;
• nausea, constipation;
• headache; or
• "hangover" effect (drowsiness the day after a dose).

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

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Interactions

Before taking phenobarbital, tell your doctor if you are using any of the following drugs:

• doxycycline (Adoxa, Doryx, Mondox, Oracea, Vibramycin, and others);
• other seizure medications such as divalproex (Depakote), phenytoin (Dilantin), or valproic acid (Depakene);
• an MAO inhibitor such as isocarboxazid (Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or tranylcypromine (Parnate);
• griseofulvin (Grisactin, Fulvicin PG, Grifulvin V);
• birth control pills or estrogen hormone replacement, including estrogen (Premarin), estradiol (Estrace, Femtrace, and others), progesterone (Progest, Prometrium), and others;
• steroids such as prednisone (Orasone, Deltasone), prednisolone (Prelone, Delta Cortef), methylprednisolone (Medrol), and others.

This is not a complete list and there may be other drugs that can interact with phenobarbital. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

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